"System.PlatformNotSupportedException: Microsoft.Data.SqlClient is not supported on this platform." on Linux

I just started getting this error today on my Linux system, building a net6 solution on Rider - It builds but won't run. I've tried upgrading my version of Microsoft.Data.SqlClient from nuget but that's made no difference. This was working fine last week.

There are a couple of things I've done that may have broken it - I got mono working over the weekend to try and get some legacy NETFramework code building for another project, for one. The other was a global update of ef tools dotnet tool update --global dotnet-ef as I had the 5.x tools version installed.

My OS has multiple runtimes installed...

dotnet --list-runtimes                                                                                                                                               
Microsoft.AspNetCore.App 6.0.0 [/usr/share/dotnet/shared/Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 6.0.13 [/usr/share/dotnet/shared/Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 7.0.2 [/usr/share/dotnet/shared/Microsoft.AspNetCore.App]
Microsoft.NETCore.App 6.0.0 [/usr/share/dotnet/shared/Microsoft.NETCore.App]
Microsoft.NETCore.App 6.0.13 [/usr/share/dotnet/shared/Microsoft.NETCore.App]
Microsoft.NETCore.App 7.0.2 [/usr/share/dotnet/shared/Microsoft.NETCore.App]

The app builds to target 6.0.

I'm a bit lost as to where to start trying to find problems - I#ve read about the netstandard2.0 version of this library being a kind of breaking stub, but the Assembly Explorer in Rider tells me that the version of Microsoft.Data.SqlClient in my bin directory is net6. I'm not sure what I should be seeing in the runtimes directory in here - I have a unix runtime shown there but NOT a linux specific runtime - Is this a red herring or am I on to something?

I've reverted the dotnet-ef tool by uninstalling it and running dotnet tool install --global dotnet-ef --version 5.0.0 - This hasn't helped at all.

I recommend to not install dotnet from the arch or AUR repositories at all. Instead use the script provided by Microsoft. This installs the original builds.

https://learn.microsoft.com/en-us/dotnet/core/tools/dotnet-install-script

I created this wrapper script which I use any time I need to install a machine:

#!/bin/bash
# This script installs specified versions of .NET Core and the latest LTS

# Function to install a specific .NET Core version
install_dotnet_version() {
    local version="$1"
    echo "Installing .NET Core version $version..."
    curl --silent --show-error --location https://dot.net/v1/dotnet-install.sh \
        | sudo bash /dev/stdin -c "$version" --install-dir /usr/share/dotnet
}

# Install .NET Core versions
install_dotnet_version 3.1
install_dotnet_version LTS
install_dotnet_version 7.0

# Create a symlink to dotnet executable, if not present
if [ ! -f /usr/bin/dotnet ]; then
    sudo ln -sf /usr/share/dotnet/dotnet /usr/bin/dotnet
fi